1. Field of the Invention
The present invention relates to a system for continuously mixing gel fluid that will be used to transport fracturing proppant into a well formation to prop open the formation after fracturing. The system employs a dynamic diffuser to remove air from the fluid as the fluid leaves the dynamic diffuser and travels through a series of hydration tanks. High shear agitation is used to help mix the gel fluid and dilution fluid as it moves through the hydration tanks. This system allows increased hydration time and more complete hydration of the gel fluid in the limited tank space of skid, truck, or trailer mounted portable equipment than is possible with current gel mixing systems.
2. Description of the Related Art
Currently when mixing guar powder and water to form a liquid gel for use to transport fracturing proppant into a well formation, the mixing is done by a portable mixer and one or more portable hydration tanks. All of the equipment necessary to mix the gel is skid, truck, or trailer mounted so that it can be transported to the well site. There at the well site, the gel is constantly mixed, transferred to the fracturing blender, and pumped into the well bore. Because the equipment is truck or trailer mounted, the tank volume available for allowing the gel to hydrate after it is mixed with water is limited.
One of the problems with current gel mixing systems is that, without the use of large hydration tanks, the gel is not fully hydrated to the desired viscosity before the gel is transferred to the fracturing blender. Large hydration tanks can not be readily skid, truck or trailer mounted for use at a well site. Without using large hydration tanks, the gel will have a short residence time of the liquid within the smaller skid, truck or trailer mounted hydration tanks which does not allow sufficient time for the gel to become adequately hydrated before it is transferred to the fracturing blender prior to being used in the well.
The present invention addresses these problems by creating a gel concentrate, employing a dynamic diffuser for quickly removing the air from the fluid as the fluid exits the gel mixer, and by progressively diluting the gel concentrate in a series of hydration tanks to maximize hydration time without allowing the gel to become so viscous that it is not easily diluted or pumped. High shear agitation of the fluid between the hydration tanks also helps to increase the hydration rate. By progressively diluting the gel concentrate, residence time and hydration time are maximized in the limited tank space. The result of this new continuous gel mixing system is that the gel is almost fully hydrated when it is transferred to the fracturing blender without the need for an increase in the volume of the hydration tanks.
Some gels hydrate faster than others. This system is useful for both standard gels and fast hydrating gels. With fast hydrating gels, the system can be operated at a higher throughput rate, thus extending the usefulness of the system.
One object of the present invention is to provide a system that continuously mixes guar powder with water to produce a gel.
A further object to the invention is to provide a system that employs high sheer pumps that allow the guar to hydrate into a viscous gel more quickly than prior art systems. When dry guar powder is mixed with water, a thick gelatinous coating is formed around each of the particles of the dry powder as the powder begins to hydrate at its surface. These partially hydrated particles may be called micelles. They are relatively dry in their nucleus and are progressively more fully hydrated at their surface. The high sheer pumps used in the present system tend to disrupt or sheer this gelatinous outer coating off of the micelles. This allows the dryer inner portions and nucleus of the micelles to be contacted with water more quickly, thereby speeding up the hydration process.
Another object of the invention is to increase the hydration time of the gel within the limited hydration tank space.
Still a further object of the invention is to provide a system that does not require special chemicals such as non-aqueous carrying fluids, suspending agents, and dispersing agents for the process. By not requiring special chemicals, some of which are considered harmful to the environment, the end gel product is more economical and more environmentally friendly.
A final object of the present invention is to employ mobile equipment such that the equipment would be truck or trailer mounted and the gel would be produced at or near the well site using the truck or trailer mounted equipment.